1. Field of the Invention
The present invention relates to a method of manufacturing a multilayer ceramic electronic component comprising ceramic layers which are stacked with each other through internal electrodes, and more particularly, it relates to a method of manufacturing a multilayer ceramic electronic component including improved steps of forming the internal electrodes and ensuring insulation between the internal electrodes and external electrodes.
2. Description of the Background Art
It is well known that a multilayer ceramic electronic component such as a multilayer capacitor or a multilayer piezoelectric actuator comprising a plurality of ceramic layers which are stacked with each other through internal electrodes is applied to various uses. A method of manufacturing such a multilayer ceramic electronic component is now described with reference to a multilayer capacitor.
In a conventional method of manufacturing a general multilayer capacitor, conductive paste is printed on one major surface of each of a plurality of rectangular ceramic green sheets to extend from a first edge toward a second edge but not to reach the second edge, with a gap region. Then, the plurality of ceramic green sheets having the conductive paste layers printed thereon are stacked so that the gap regions are alternately positioned along the thicknesses, to obtain a laminate. Thereafter the laminate is compressed along its thickness and fired to obtain a sintered body, so that external electrodes are formed on a pair of opposite side surfaces of the sintered body respectively. Thus obtained is a multilayer capacitor, in which the internal electrodes are alternately electrically connected to the external electrodes provided on the pair of opposite side surfaces along the thicknesses.
In the aforementioned method, however, it is difficult to accurately control the gap regions between the internal electrodes and those of the external electrodes which must not be electrically connected with the internal electrodes, since the internal electrodes are formed by printing the conductive paste on the ceramic green sheets. Consequently, it is inevitably necessary to increase the widths of the gap regions, i.e., the distances between the internal electrodes and those of the external electrodes provided on opposite sides. Thus, this method has such problems that (1) distortion stress tends to concentrate in forward ends of the external electrodes, and (2) it is impossible to further miniaturize the multilayer capacitor.
On the other hand, Japanese Patent Laying-Open No. 2-224311 (1990) proposes a method of electrochemically etching a sintered body for partially dissolving/removing the same thereby forming gap regions, so that widths of the gap regions can be controlled in high accuracy. According to this method, conductive paste is printed on the overall surface of each of a plurality of ceramic green sheets to form an internal electrode, and the plurality of ceramic green sheets provided with the conductive paste layers are stacked with each other to obtain a laminate. Then the laminate is sintered, and thereafter a pair of opposite side surfaces of the sintered body as obtained are electrochemically etched with respect to the internal electrodes which must not be finally exposed on the opposite side surfaces, so that portions exposing the internal electrodes and those close thereto are dissolved/removed to define clearances. The clearances are filled up with an insulating material such as synthetic resin, and thereafter external electrodes are formed on the pair of opposite side surfaces respectively.
According to the method disclosed in Japanese Patent Laying-Open No. 2-224311 (1990), it is possible to narrow the aforementioned gap regions since the internal electrodes which are exposed on the pair of opposite side surfaces of the sintered body are electrochemically etched to define clearances as hereinabove described.
In this method, however, the electrodes are formed by printing the conductive paste and baking the conductive paste in firing of the ceramic green sheets. Thus, the electrode material is so insufficient in continuity that edges of the forward ends of the internal electrodes facing the gap regions are not necessarily sufficient in smoothness. When the widths of the gap regions are narrowed in the sintered body, therefore, electric field concentration easily takes place in parts of the insulating material which is filled up in the clearances, to cause dielectric breakdown.